This invention, which has both civilian and military values, pertains to a stealth, layer-effective (or layer-effect), sealing-reaction (stealth-reaction) liner, useable adjacent the inner surface area of a vehicle's synthetic-fuel tank, and structured to provide a rapid and robust, self-sealing, anti-leakage reaction to a tank-wall puncture wound, such as a bullet wound. More specifically, this invention pertains to such a liner which is designed, until such a puncture wound, or breach, occurs, and although always in direct “normal” contact with synthetic fuel, to be normally “dormant” within the fuel-containing tank environment in what might be thought of as a “stealth mode”, but which is effective immediately, through interactive reaction to and with breach-produced, leaking fuel, to react, in a realm within the liner formed as an inner, or central, initially shrouded layer region containing synthetic-fuel-reactive liquid-imbiber beads, to such leakage quickly to seal such a wound.
A preferred and best-mode embodiment of the invention is described herein generally in a military setting, and in relation to a particular, illustrative, synthetic vehicle-motor fuel referred to as FT synthetic fuel, made by a South African company named Fisher-Tropsch—a fuel which is now being used in many military-vehicle fuel tanks.
The invention specifically takes its very useful place in an environment where, as is now progressively the case, conventional “natural” motor fuels are being replaced by synthetic fuels.
It has been conventional practice in the past to line military fuel tanks with an inside lining, or bladder, formed of a defined-thickness natural rubber material, and always, heretofore, in the context of the relevant container being one which holds conventional, or “natural” engine fuel. In such a setting, it is the practice to furnish an additional barrier layer which resides between the natural-rubber lining, or bladder, and the fuel, and specifically a barrier layer formed of a material which is nonreactive with regard to conventional natural motor fuel, in order to isolate the natural-rubber lining from direct, normal contact with fuel contained in such a tank.
With regard to puncture wounds created in such a setting, i.e., one where natural petroleum-based fuel is employed, it is definitively the case that, when a puncture breach occurs (a) in such a tank, (b) in the natural-rubber tank lining structure, per se, and (c) in the lining-protective barrier-layer material (thus to expose the natural-rubber lining structure to direct contact with that fuel), leaking fuel successfully reacts with the natural-rubber lining to initiate a reaction which is usually effective to seal such a wound.
However, and as has been suggested above, there has recently been developed a synthetic fuel, such as the synthetic fuel known as the above-mentioned FT synthetic fuel which changes the picture regarding this conventional fuel-leakage issue. To the surprise of everyone involved with decisions implemented to utilize this synthetic fuel, this fuel does not react with conventional natural-rubber-based anti-leakage liners on the occurrence of a puncture wound to invoke the anticipated liquid-imbibing and material-swelling wound-sealing action.
Explaining at this point certain terminology and phraseology which we employ herein, and to some extent have already employed above, the terms “stealth” and “stealth-reaction” are used to emphasize the fact that our liner, i.e., its body, is, until breached by a wound which exposes the above-mentioned, special, normally shrouded, internal “layer region” possessing the also-mentioned liquid-imbiber beads, inherently “silent” about its capability to respond to the onset of a fuel leak. Normal direct exposure of the un-breached (i.e., not yet penetrated) liner body does not trigger a response reaction. The liner does not, as distinguished sharply from structures in the prior art, require the added material cost, the added labor cost, and/or the added fuel-tank room-occupancy “cost” of any additional “guard” barrier against normal fuel contact.
Additionally, we refer to our liner as being “layer-effective”, or as possessing a “layer-effect”, in order to point out that while the liner body can be viewed as possessing layers, or regions, (preferably three) which furnish distinct, differential, but layer-cooperative, performances, the internal interfaces between these regions preferably (though not absolutely necessarily) take form of material continuities (i.e., no discontinuities) respecting the main elastomeric material which defines the principal, constituent element of the liner body. An important consequence of this preferred, “material-continuity” construction is that the entire body of elastomeric material responds with cooperative, distributed compression and tension, as dictated by wound-healing circumstances, when a wound exposes the central liquid-imbiber beads to fuel contact, with such contact producing the immediate result of rapid fuel imbibing and material swelling by the beads to seal the wound and stop fuel leakage. The entire transverse (across the layer regions) body portion of liner elastomeric material adjacent such a wound is, under leak-reaction circumstances, in compressive and tensive cooperation in aid of wound closure and sealing. Layer regions on opposite sides of the central, imbiber-bead-containing region, function as cooperative, compression-aiding regions enhancing the swelling, leak-sealing action which is created in the central liner region.
The present invention addresses the synthetic fuel-leak situation by proposing a unique, inside-tank (container), rubber-based (pure natural, or blended), or alternatively polyurethane-based or polyurea-based, liner which is designed specifically to react, as a result of a puncture wound, with synthetic FT fuel to create the desired liquid-imbibing and material-swelling wound-sealing actions. This newly proposed lining has the mentioned “stealth” characteristic, which, without requiring any additional barrier-layer material, and with the liner per se thus normally being fully in contact with tank-held synthetic fuel, prevents the liner from reacting normally, unexpectedly, and undesirably with such fuel, and does so until a leak-creating puncture breach occurs in the relevant tank wall and the liner body.
The liner of this invention fundamentally, and in its preferred and best-mode form, takes the form of a functionally layered (a layer-effective) body structure, preferably without any distinct inter-layer discontinuity boundaries, or distinct interfaces, which includes (a) at least two outer layer regions formed of pure natural rubber (or a natural rubber blend) without any additives, and (b), effectively sandwiched between these outer layer regions, an intermediate layer region which (1) utilizes the same outer-layer-region “rubber” material, but which (2) also includes an embedded plurality of synthetic-fuel-reactive liquid-imbiber beads, such as those identified with the product designator IMB230300, made by Imbibitive Technologies America, Inc. in Midland, Mich.
In this newly proposed liner structure, since the basic liner material per se, that is, the material other than the embedded imbiber-bead material, is nonreactive directly to synthetic fuels, it may be placed, without any additional barrier structure, directly inside a fuel tank, normally against the inside surface, or surfaces, of the wall of that tank, and be normally fully exposed to synthetic fuel contact, without there being any risk of an undesirably triggered interaction between the synthetic tank fuel and the liner. An extra installation of a protective barrier structure is, accordingly, not required. It is only when a puncture wound occurs that exposes the inner (imbiber-bead) layer region of this liner to fuel leakage, that a reaction occurs between leaking fuel and the then exposed imbiber beads.
This reaction triggers a liquid-imbibing and material-congealing swelling action which rapidly functions to close the leak-initiating wound. The layer regions of liner material which are disposed on opposite sides, so-to-speak, of the central layer region which contains the liquid-imbiber beads, function, once a fuel-contact reaction begins with the liquid-imbiber beads, to furnish a compressive pressure around the area where reaction is occurring, thus enhancing the sealing ability of the liner structure.
As an illustration of one of a variety of appropriate manufacturing ways, an expanse of this newly proposed liner material may be created by the production of (1) independent, suitably thick mats of pure natural (or blended) rubber material, and (2) independent, suitably thick mats of the same natural or blended rubber material which are imbiber-bead-imbedded, which independent mats are then pressure-and-heat-consolidated into a unified, three-effective-layer lining structure. Pressure and heat consolidation function to “weld” the three layer regions into a unit lacking material discontinuities between the layer regions The assembled liner structure is then edge cut to appropriate shapes for fitting against the inside wall(s) of a selected fuel tank/container.
Another production approach which could be used, and which will create a modified form of liner, involves the use of not necessarily a natural (or blended) rubber material, but rather of an elastomeric polyurethane or polyurea material, and particularly such a material which is susceptible to casting in stages that are effective to build a layered structure such as that which has just been generally described where natural, etc. rubber is employed. Casting of plural layer regions, with appropriately shortened timings maintained between casting “pours”, results in chemical interfacial bondings occurring between these regions to create the preferred, desired liner-body material continuity.
The various features and advantages which are offered by the liner structure of the present invention will now become more fully apparent as the description which shortly follows is read in conjunction with the accompanying drawings.